This invention relates to a pick and place apparatus, in particular to such an apparatus for use in a die attachment operation in semiconductor manufacturing processes, and more particularly still is directed to such an apparatus that is capable of operating at high speed and with high precision.
Pick and place apparatus are used in a number of operations within semiconductor manufacturing and assembly processes. As the name implies, a pick and place apparatus functions to pick a component from one location, and then place it in a second location.
One example of such apparatus is used in a die attachment operation. In such an operation a pick and place apparatus is used to pick a die from a delivery mechanism, and then transfer the die to a desired location on, for example, a printed circuit board and place the die on the board. The apparatus may also carry out a bonding operation.
It will be appreciated that the speed of the die attachment operation is dependent on the speed with which the pick and place apparatus can function to accurately pick a die and place it in the desired location on the circuit board. Unfortunately with ever smaller dies and ever more accurate placement being necessary, problems arise as a consequence of the competing needs for speed and accuracy.
FIG. 1 is a perspective view of a pick and place apparatus according to the prior art. The apparatus comprises a bond arm 1 that is adapted to move both vertically (ie in the Z axis) and rotationally about the Z axis through an angle xcex8. Both the vertical and rotational movement is effected by means of a motorized actuator unit 3 which enables the bond arm 1 to rotate through 90xc2x0 about the Z axis.
The bond arm comprises two main parts that are interconnected by a pivot joint 2 such that the main part of the bond arm 1 can swing about the Y axis with respect to the rear part 5 of the bond arm. This enables a pick tool 4 to be movable vertically with an adjustable bonding force that is set by a pre-loaded spring 7.
With such apparatus the pick operation in which a die is picked from some form of delivery system, and the subsequent placement and bonding operations, are all performed using vertical movement in the Z direction, either by movement of the whole bond arm by the actuator 3, or by swinging movement of the bond arm 1 about pivot 2. However, between the pick operation and the placement and bonding operations, a transfer operation is carried out that involves rotary movement about the Z axis. In this operation a die is transferred from the pick location to the placement location.
A difficulty arises, however, with high speed operation. If the bond arm is rotated about the Z-axis at high speed, it must be stopped rapidly at the ends of its travel. This sudden stopping of the bond arm causes substantial vibrations in the bond arm that result in a placement error. This is particularly problematic when the bond arm has been moved to transfer a die from the pick location to the place location where a very high degree of accuracy is required. In practice, the placement and subsequent bonding operations cannot be performed until the vibration of the bonding arm caused by the sudden stopping of the rotary movement has died away.
In other words, any gains in operational speed from high speed rotary movement of the pick and place apparatus are, at least to a degree, lost by the fact that the consequential vibrations must be allowed to die away before the placement and bonding operations can be performed.
According to the present invention there is provided a pick and place apparatus comprising a pick and place member adapted to pick an electronic component from a first location and to place said component at a second location, wherein said pick and place member is formed with a cavity within which cavity are located a plurality of damping particles for damping unwanted vibrations of the pick and place member.
Preferably the particles are irregular in shape, for example they may be tungsten granules, with a diameter in the range of between 0.3 and 1.2 mm. The particles may fill the cavity with a filling ratio of about 75% by volume.
In a particularly preferred embodiment the pick and place member may be a bond arm that is adapted for rotation about an axis, and the cavity is formed at an end of the bond arm remote from the axis.